Automotive Air Conditioning Information Forum (Archives)

Provided by www.ACkits.com

We've updated our forums!
Click here to visit the new forum

Archive Home

Search Auto AC Forum Archives

70 deg vent air on 90 deg day Pages: 12

Airstream on Thu July 21, 2011 10:32 AM User is offlineView users profile

I’m slowly trying to figure out why my '84 Suburban C20 (454, dual-air, R134a, CCOT, A6 compressor) will not keep us cool on long trips. The other day, it was 90 degrees in the shade where the truck’s cold engine was. I hooked the gauges up, and the static pressure agreed with the ambient temperature.

The engine was then started with the auxiliary electric radiator fan on, and the A/C on max (recirc). A minute or two later, 80 degree air was blowing out of the dash’s center vent. The fan was OFF on the rear air handler. I had hoped for cold air since the whole truck was at ambient.

For some reason, the high-side hose decided to leak at the manifold, and could not be fixed. The engine was switched off, and few minutes later the hose was detached from the high side.

After letting the engine warm up on high idle to the point that the fan clutch engaged (supplementing the electric fan), the high side pressure was steady at 51 psig, and the compressor outlet measured 142 degrees. According to my chart, the pressure would have been ~235 psig. The vent temperature got no lower than 71 degrees. Switching the rear A/C fan on raised the pressures to 51 psig & 150 degrees (263 psig).

Oddly, not only was the accumulator sweating like a pig, so was a lot of the compressor.

Since the system is not cycling, I don’t think it is LOW on R134a. The next step, after I get a new high-side hose, is to vent some refrigerant, and see if cooling improves. If cooling does not improve, then I have to suspect the compressor is not working hard enough for some reason.

What part of my A/C’s system would you suspect?

Thanks,
Tom

bohica2xo on Thu July 21, 2011 12:46 PM User is offline

Quote
Originally posted by: Airstream




What part of my A/C’s system would you suspect?



Thanks,

Tom

Pretty much the whole system is suspect. It is an unknown 134a conversion, with no high side pressure readings. It could have 3 oil charges in the system, or be almost empty. The R12 dessicant bag may have burst. Fan clutch may be dead.

I can tell you that the A6 should not be frosting up on the case.

Get a set of gauges on it, and run it at 1500+ engine rpm with the doors open. Both cabin fans on highest speed. Post the pressures. We can go from there.

B

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Airstream on Thu July 21, 2011 1:42 PM User is offlineView users profile

Quote
Originally posted by: bohica2xo


... I can tell you that the A6 should not be frosting up on the case.

Yeah - the sweating compressor certainly caught me off guard. I'm suspecting too much oil in the system as a possible cause.

I hope to have a new high-side hose soon.

Tom

Airstream on Fri July 22, 2011 9:09 AM User is offlineView users profile

Quote
Originally posted by: bohica2xo

Get a set of gauges on it, and run it at 1500+ engine rpm with the doors open. Both cabin fans on highest speed. Post the pressures. We can go from there.
I hooked up the gauges last night with a new seal on the high-side hose connection. The weather was cloudy, humid, and 80 degrees. Static pressure reflected the ambient temperature.

After the engine was started & running at medium idle the low-side/high-side reading was 62/165 with a little bit of compressor noise. Center vent temperature was 71.5 degrees. Front and rear fans on high; front selector on MAX.

Three or four minutes later there was no noise, both the accumulator & compressor were sweating, and pressures were 54/189 with 68.9 degree vent air.

A few minutes after that, the engine is still not warm enough to engage the fan clutch. But the supplemental electric fan was on. Pressures were 60/260 with 71.4 degree vent air.

Minutes later, pressures were 68/320 with 75 degree vent air.

A few minutes later at about the time I expected the fan clutch to engage, the high-side gauge hose blew a crimped fitting.



I was sitting in the driver’s seat when that occurred, and immediately switched the compressor off before getting out to see what happened. The engine immediately went to HI idle, and the clutch fan engaged.

Based on the above readings, why is my truck’s A/C not cooling any better than it is?

Thanks,
Tom

bohica2xo on Fri July 22, 2011 10:18 AM User is offline

Lucky you were in the cab. Could have cost you an eye when that let go @ 320+ psi. What brand was that hose?

The up side to this is now we know there was a lot of oil in the system. Those pressures, along with the mess underhood kind of point to a no-flush 134a conversion.

Your fan clutch sounds like it is tired. A good clutch should move enough air on the viscous drive to keep up with things at idle loads. It should roar on a cold start, and blow your hat off. Hopefully you have a fan shroud in place, and it it not missing any huge chunks.

Might as well break the system down now & start from square one. The A6 has a sump, and much of the oil in that system should stay at the compressor. decades ago, the Delco / Harrison rep told us 10% of the weight of the refrigerant charge was "right" for the A6 system's oil charge. Of course back then we would check the oil level on an A6 by cracking the sump plug on a charged system...

I will look for an old book oil charge for that vehicle for you. Flush back to bare metal in the lines & evaporators. Consider upgrading the condensor. Replace the dryer.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Airstream on Sat July 23, 2011 5:02 AM User is offlineView users profile

The manifold gauge set was made by Interdynamics.

"Back then" when you checked the oil level by cracking the sump plug, just what were you verifying? The plug appears to be on the bottom, and appears useful only for draining the sump. What am I missing?

Thanks for looking around for an old oil capacity reference- I've gotten a lot conflicting information on how much oil this system is supposed to hold.

Tom

Airstream on Sat July 23, 2011 10:14 AM User is offlineView users profile

Interestingly, I drove the Suburban down to the quarter-carwash this morning to wash all the oil out from under the hood before doing anything else, and the air conditioner still worked & did not appear to cycle. Vent temp was 70 degrees, ambient 80.

After getting home, I popped the hood to find the compressor still sweating like it was before the hose blew. So I guess the system still has too much oil in it.

Tom

Edited: Sat July 23, 2011 at 10:15 AM by Airstream

iceman2555 on Sat July 23, 2011 10:39 AM User is offlineView users profile

There are two aspects of a successful AC repair and diagnostic of a performance (cooling) concern, the amount of refrigerant (fully charged) and the amount of lubricant within the system. Not knowing these values makes for a 'guess-ta-mation' of performance and pressures. To make a valid diagnosis, flush the system....as bohica states...'back to the metal'. Use a good quality flush chemical and air purge to insure removal of all traces of flush. Add the correct amount and type of ac lubricant. Suggest to use a DEC PAG 150 for this system. Insure that the system is fully charged....not the use of several cans and a derived pressure....get the system charged so that one knows the correct quantity of refrigerant. Start with app 90% 134a to 12 specs. Forget the issue of pressures.....they are basically meaningless with a retro fitted system.

A good test for proper charge with this system is to charge with the suggested amount. , Operate the system for app 10-12 minutes with the vehicle @idle, max cool (recirculate),coors open, blower on high. Both front and rear systems should be engaged. Once the system has had time to 'stabilize' determine the inlet and outlet temps of the evaporator. The test should be taken after the orifice tube and before the accumulator inlet. These temperatures should be within 3-5 degrees of each other. A outlet temperature that exceeds the inlet by more than 6-8 degrees requires additional refrigerant. If charge rates are adjusted...the system should be allow to 'stabilize' once more prior to additional testing.

Once more agreement with bohica concerning the fan clutch. A fan clutch should never completely disengage. Clutch engagement is determined by the temperature of the air flow between the radiator and fan clutch temp sensor (face of clutch). A start up the clutch should be heavily engaged and should moderate after a few minutes of operation. Considering the operational time and pressures associated with this test, there should have been good solid clutch engagement. Suggest to disengage the 'supplemental' fan to insure the OE system is functional correct. Then re establish the 'supplemental' fan. This extra fan is a very good idea for retro fitted system...esp when the OE condenser is being used.

Once the system has been serviced, re test all temperature...evap....condenser (inlet and outlet).....vent temps ...ambient temps and post results.

Pressures are good for testing...but surface temps of the heat exchangers are as important. One down side of temp testing...the cost factor. Laser or infra red are almost useless for this procedure. There are several multi-meters on the market that allow for a temp test probe that are 'not break the bank' tools. A good test tool can be purchased from UEI, the single channel is great for basic testing and is quite affordable. Spend the extra cash and obtain a touch type thermo coupler. Their dual channel is a good upgrade. Not sure if site sponsor has access to this tool, but check with them....I am sure they will try to offer a good temp test tool.

Get the system properly serviced and then re evaluate the system.

The issue of the compressor 'sweating' is not that uncommon in some of the earlier vehicles. Lubricant is not the cause....it is the charge rate or flow of refrigerant. The inlet temps of the compressor are cooled (low pressure) to the point that in high humidity areas...they sweat. This was not that uncommon in the A6 mounted on GM or Ford platforms. Not a 'everyday occurrence'...but did happen now and then.

Back to getting the system properly serviced.....and then evaluated.

Good luck.

-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

Airstream on Sat July 23, 2011 12:47 PM User is offlineView users profile

Quote
Originally posted by: iceman2555
...A good test for proper charge with this system is ... max cool (recirculate),coors open, ...
I'm a Natural Lite man myself - there's one open now while the refrigerant is being recovered.

On a serious note, THANKS! for the outstanding post. Your words, and those of bohica are exactly what I was hoping to read on this forum.

Next planned step is oil removal. Both of you recommended a flush. GM had a bulletin out concerning R12 to R134a conversion which advised against flushing. If the oil recovered by simply cracking fittings looks clean, do I really need to solvent flush?

Tom

bohica2xo on Sat July 23, 2011 1:34 PM User is offline

Huh, that is a new twist on the ID death kit. Buy a decent Manifold set and save yourself a lot of trouble. That link is for a good solid unit, under a hundred bucks. If the hose was that bad on that ID unit, what else is wrong with it?

Why are you continuing to run a system that has had a catastrophic leak?

I checked my 1985 printed copy of system specs, and the oil charge is listed as 10 ounces. You should put the whole 10 ounces in the compressor sump.

As for checking the oil level, older A6's had a fill plug on the side of the sump. If you have an old (60's vintage) service manual it will have a picture of a wrench on the plug & a description to "look for a drop of oil". Not recommended now of course.

You really need to tear that system down & fix it before you run it any more.


Iceman:
He has a couple of threads on this vehicle here. It is probably way overcharged on oil, sounds like it got 19 ounces of PAG or POE added to the remaining mineral oil charge when it was converted. Nothing is going to change until he opens the system & starts from square one.

B.




-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Airstream on Sat July 23, 2011 2:23 PM User is offlineView users profile

Quote
Originally posted by: bohica2xo
...Why are you continuing to run a system that has had a catastrophic leak?

...You really need to tear that system down & fix it before you run it any more.
I ran it for a short time out of nothing more than curiosity. In spite of the oily mess under the hood, I figured the sump and/or accumulator still had oil so the compressor would be okay. My personal experience with this truck is that there is a mechanical device in the accumulator (independent of the pressure switch) that will not allow the system to run should the refrigerant drop too low. Obviously, I could be wrong.

As I type, the refrigerant is being recovered from the system. If there was not an acre of grass that needs cutting right now, I's start on system tear-down shortly. Hopefully I will start recovering the remaining oil tomorrow.

Please do not get the wrong impression - I really appreciate your posts & help in getting my primary tow vehicle back on the road.

Tom

JJM on Sun July 24, 2011 12:06 AM User is offline

Quote
The manifold gauge set was made by Interdynamics.

Well that explains it then. Not suprising though.

Anytime you have a major high side blowout like that, you've lost a lot of oil.

Joe

When considering your next auto A/C purchase, please consider the site that supports you: www.ACKits.com

edahall on Tue July 26, 2011 4:09 PM User is offlineView users profile

Quote
Originally posted by: iceman2555

Pressures are good for testing...but surface temps of the heat exchangers are as important. One down side of temp testing...the cost factor. Laser or infra red are almost useless for this procedure. There are several multi-meters on the market that allow for a temp test probe that are 'not break the bank' tools. A good test tool can be purchased from UEI, the single channel is great for basic testing and is quite affordable. Spend the extra cash and obtain a touch type thermo coupler. Their dual channel is a good upgrade. Not sure if site sponsor has access to this tool, but check with them....I am sure they will try to offer a good temp test tool.




iceman2555,

Why isn't an infra red thermometer useful in the procedure you described?

Thanks,
Ed

iceman2555 on Tue July 26, 2011 5:29 PM User is offlineView users profile

Infra red and laser type test units have proven to be inadequate for measuring temperatures in heat laden areas such as engine bays. They are great for some testing, but we have found over a period of time that a good thermometer with couplers(clamp or touch) is much more efficient when diagnosing an AC system. We have seen test readings that vary as much as 50-60 degrees.

-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

Airstream on Tue July 26, 2011 8:46 PM User is offlineView users profile

Quote
Originally posted by: JJM
Quote
The manifold gauge set was made by Interdynamics... Well that explains it then. Not surprising though
I'm learning more in this forum than I really wanted to in what is my first real foray into servicing auto A/C.

In all fairness, I bought the manifold gauge probably 16 years ago because the auto parts store was dumping it for little or no money because the gauges & fittings were only R12 compatible.

After the blowout, the crimped end was cut off, and a hose clamp was used to hold the hose onto the barbed fitting.

Earlier this evening, I tried to use the manifold while recharging my Suburban. The high-side hose did not blow off, but it started hissing & blowing out the new oil I just added before the pressure really got that high. Recharging was immediately stopped before the full charge was added, and the red hose disconnected. Before that, though, vent temps were looking good, and the compressor was not sweating although the accumulator was.

I'm torn now. The maniflold's valve stems do not appear to leak, and I'm inclined to just buy new hoses. But NO ONE, except me will ever service my Suburban again while I own it, and I'm sure that more A/C work will be required.

Tom

JJM on Tue July 26, 2011 10:27 PM User is offline

Still can't believe all the oil that was recovered, depsite the hose blowing out. You had more oil in there than some OPEC countries have under the sand. Pretty amazing.

Seriously though, get yourself a good set of gauges or you'll just end up with lots of frustration. Site sponsor has a wide variety of quality gauge sets.

Joe

When considering your next auto A/C purchase, please consider the site that supports you: www.ACKits.com



bohica2xo on Wed July 27, 2011 1:46 AM User is offline

Tom:

That link I posted before is a nice, affordable gauge set. Not the top of the line, but a unit we all trust here. Since you just found out how many people here got started doing their own A/C (dishonest mechanics), take it from someone who has been where you are at - and buy a decent manifold set.

We are all volunteers here, but we do tend to recommend the site sponsor. That link does go to the site sponsor, but buy from whoever you like. Just buy a decent gauge set.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Airstream on Wed July 27, 2011 7:15 AM User is offlineView users profile

Quote
Originally posted by: bohica2xo
… Just buy a decent gauge set.

You’re right Brad. If nothing else, last night I kept worrying if my cheezy tethers were going to hold up against another incident. My attention should have been elsewhere.





‘Tim R. Bohringer’ also probably appreciates you urging me to do the right thing – I just got an auto-email with his name on it from Arizona Mobile Air thanking me for shopping there this morning.

Tom


TRB on Wed July 27, 2011 12:39 PM User is offlineView users profile

Thanks for the support. Helps to keep things running around here.


-------------------------

When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

tony1963 on Wed July 27, 2011 8:39 PM User is offline

Basically, you need to tear down the whole system and start over. The old style condenser can be flushed and so can the front evaporator.

Install a new orifice tube and drier. Vacuum down the system for about an hour. Then, add the refrigerant oil in the proper amount followed by refrigerant.

It is not going to blow ice cubes, but it will keep you cool. I have an 85 model with an entire retrofit and it does just fine.

-------------------------
Grove Automotive Group, Inc.

An Alabama Corporation

Airstream on Thu July 28, 2011 9:55 AM User is offlineView users profile

Quote
Originally posted by: iceman2555
...get the system charged ... Start with app 90% 134a to 12 specs. Forget the issue of pressures...

A good test for proper charge with this system is to ... determine the inlet and outlet temps of the evaporator. ... An outlet temperature that exceeds the inlet by more than 6-8 degrees requires additional refrigerant...
Iceman - What is the "do not exceed" point for adding R134a to this system? 100% of the R12 spec? 105%?

I went ahead & recovered the R134a I put in the system before the hose starting leaking so I could get a fresh start on adding the correct charge when my new set of gauges arrives.

Although you said to forget about pressures, I figure that meant for pressures that weren't going to hurt anything. What pressures might show up that mean "Stop what you are doing NOW!"

Thanks,
Tom

bohica2xo on Fri July 29, 2011 2:50 AM User is offline

One of the requirements for a 134a conversion is the HPCO. That switch should drop the compressor out around 400 to 420 psi.

Obviously if it is cycling on the HPCO, you have a problem. What Iceman means is you need the full charge in the system to operate properly, and sometimes that means pressures that are higher than they were with the original R12 charge. That "80%" number was intended to hold the pressures down to near R12 levels.

Since your rear system is an aftermarket unit, the charge levels are a big unknown anyway. I suspect the system may hold more than an OEM rear because of plumbing differences. You will need to watch the pressures, and monitor the evaporator line temperatures for optimum performance.

Don't be surprised by high side pressures that are more than 3x the ambient temperature during full load testing.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Airstream on Tue August 02, 2011 6:29 PM User is offlineView users profile

The new gauge set arrived just a little while ago.



Although it has yet to be hooked up to the Mighty Suburban, I am incredibly impressed with what I see in comparison to the last set of gauges I had. Although the manifold appears similar in appearance to what I had, the hoses/fittings appear to be of a quality head-and-shoulders above what blew out before. Mastercool's hose description, if nothing else, reads better than than the lack of description the last set had. If nothing else, the new hoses had a better "feel" to them (as in not potentially blowing apart later) than my last set. It will be nice to have gauges with R134a markings.

To be honest, I ordered this particular item from Tim because of Brad's posts about having the right equipment to do the job got to me. I'm not used to the abuse (I've yet to make a mistake...ever...just ask me). But Brad gets a big thumbs-up on this one. Tim does too for making it available.

If nothing else, I never even noticed the package was supplied with 72-inch hoses when it was ordered. It's just a bonus day here in AL.

I expect great results tomorrow or the next day. But if that does not happen, it won't be because of faulty test equipment.

Tom

JJM on Tue August 02, 2011 10:37 PM User is offline

I've never regretted spending money on good tools... it's only when I've cheaped out did I have regrets. And you've definitely purchased from the right place.

I still have my original R-12 gauge set that I first started out with sometime in the early 1980s. The low side hose still has gouges from dancing on the fan of a Lincoln 460 V-8 (those things had such thin shrouds), but it's still good. I do have a replacement hose, still brand new, haven't had the need for it. That gauge set has gotten knocked around quite a bit and is still going strong.

Joe

When considering your next auto A/C purchase, please consider the site that supports you: www.ACKits.com



bohica2xo on Wed August 03, 2011 2:34 AM User is offline

Aye, that's the ticket. Always nice to have the long hoses - makes duct taping the gauge set to the windshield so much easier!

As for "taking the abuse" - I thought all Airstream owners were used to it. Now the guy with a vintage IHC Travelall towing a vintage Airstream? He is just a glutton for punishment.

Having a gauge set you trust takes the guesswork out of things like setting the cycling switch. Nothing like a 10 psi error in a gauge set to make you think there is a cooling issue when a simple cycling switch problem is making 60f vents.

Hopefully the rest of the repair will go smoothly for ya.

B.



-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Back to Automotive Air Conditioning Forum

We've updated our forums!
Click here to visit the new forum

Archive Home

Copyright © 2016 Arizona Mobile Air Inc.